...As the world marks the 10th anniversary of the war in Iraq, essays assessing what happened in that conflict and the “lessons learned” abound. But the lessons drawn are likely to tell much more about how Americans feel about their place in the world today than what really happened a decade ago.

As a practicing historian, I know how historians practice. Rewriting history is our stock and trade.

There are only two reasons to restate the past. The first is the recovery of important new information. In 1974, for example, the U.S. and British governments acknowledged the Ultra secret: that for much of World War II, the allies had been able to read the top secret messages of both Germany and Japan. That revelation sent scholars back to rewrite, because new accounts were needed to interpret what the allies did based on what the allies really knew.

The second rationale for rethinking the record is to accommodate how those in the present think about the past. Every generation has its own questions. Those questions usually tell us more about us, however, than they do about the past. In the aftermath of Vietnam, for example, there was a wave of bitter revisionism that trashed America’s participation in every war. Even the World War II, the “good war,” came in for its share of bashing....